| 摘要 |
PROBLEM TO BE SOLVED: To obtain a three-group zoom lens constituted of five lenses having a variable power ratio such as about 2, made excellent in aberration, and realizing the speed-up of focusing and the miniaturization of an optical system by adopting a rear focus system while appropriately setting the position of an exit pupil from an image pickup surface, and further satisfying specified lens shape and a conditional expression. SOLUTION: Negative, positive and positive lens groups G<SB>1</SB>, G<SB>2</SB>and G<SB>3</SB>are arranged in order from an object side. At the time of varying power from a wide angle side to a telephoto side, the lens group G<SB>1</SB>is moved to relatively come close to the lens group G<SB>2</SB>and the lens groups G<SB>2</SB>and G<SB>3</SB>are moved to the object side. At the time of focusing from infinity to a short distance, the lens group G<SB>3</SB>is moved to the object side. At the time of infinity focusing, the space between the lens groups G<SB>2</SB>and G<SB>3</SB>is nearly constant at the time of varying power. A first lens L<SB>1</SB>and a third lens L<SB>3</SB>have aspherical surfaces. The zoom lens in particular satisfies the conditional expression (4) 0.08<D<SB>2</SB>W/f<SB>3</SB><0.15 (f<SB>3</SB>means the focal distance of the lens group G<SB>3</SB>, and D<SB>2</SB>W means the space between the lens groups G<SB>2</SB>and G<SB>3</SB>at the time of infinity focusing at the wide angle end). COPYRIGHT: (C)2003,JPO
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